Alarm system



M. "r. WORKS ALARM SYSTEM Filed June 29, 1949 mm v f M W987 5 m WV MIfiI I M I f- M 1 U I I U I N W J J g 7 M 5 a w a J l] a 0 a W.

Sept. 7, 1954 A TTORNEYJ Patented Sept. 7, 1954 UNITED STATES PATENT OFF I CE 3 Claims.

This invention relates to improvements in low pressure alarms and anovel valve mechanism therefor and refers more particularly to a systemfor giving an alarm when the pressure within a gas pressure system dropsbelow a predetermined limit.

In many fluid pressure systems, it is customary to employ an alarm toindicate a drop in pressure within the system below some predeterminedminimum to facilitate maintenance of satisfactory pressure levels withinthe system. These alarms are of two general types, one type beingelectrical and the other type being fluid operated. While electricalalarms operate with a degree of satisfaction, they are expensive andtheir opera tion necessarily depends upon a source of electric currentwhich is not always reliable or readily available. Mechanical orpressure actuated alarms have been devised which are reliable from thestandpoint of giving the alarm but which are objectionable as wastinglarge volumes of pressure fluid and also in requiring a manual resettingof the alarm each time it is actuated.

An object of this invention is to provide an alarm for pressure systemswhich is actuated by the pressure of the gas in the system, which isfully automatic in giving an alarm when the pressure drops below normaland resetting when the pressure within the system is restored to normal.

Another object is to provide an alarm for pressure systems which isactuated by the pressure in the system and which is very miserly of thegas of the system.

A further object is to provide an alarm for pressure systems wherein thealarm employs a novel valve assembly which in operation, upon occurrenceof predetermined low pressure conditions within the systems willalternately open and close and which thereby permits escape of only asmall amount of the gas of the system pro tected.

Still another object is to provide an alarm for pressure systemsemploying a novel valve assembly wherein the main valve controlling flowthrough the alarm is forced open by resilient means when the pressurewithin the systems falls below a pre-selected value and is then closedby a separate pressure actuated means.

A still further object is to provide an alarm for a pressure systemwhich will provide a continuous alarm when the pressure in the system isbetween pro-selected low pressure limits and will automatically closewhen the pressure within the system is outside these limits.

Yet another object is to provide a valve assembly for controlling flowthrough a conduit in response to the upstream pressure in the conduitwherein the valve member is urged toward seated position by the pressurecontrolled and is unseated by a resilient means when the pressurecontrolled falls below a pre-selected value and additional means,responsive to the pressure controlled, is provided to reseat the valvemember when the controlled lected value.

Other and further objects of this invention will appear from itsdescription.

In the accompanying drawings, which form a part of the instantspecification, are to be read in conjunction therewith and wherein likereference numerals indicate like parts in the various views:

Fig. 1 is an elevational view, partially in vertical section, of analarm illustrating an embodiment of this invention; and

Fig. 2 is a sectional view, upon an enlarged scale, showing the detailsof the novel valve assembly of the device shown in Fig. 1.

The device shown in the drawings is a whistle type alarm adapted to givea shrill whistle when the pressure within a pressure system drops belowa predetermined value. The alarm is such, that when the pressure withinthe system protected returns to a value above the set point for thealarm, the control valve of the alarm will automatically close and thewhistle will stop blowing.

The device comprises parts forming a conduit connectable to the pressuresystem to be protected. These parts include a coupling 5 having athreaded socket in its lower end adapted to be connected to a pressuresystem to be protected. The other end of the coupling 5 is also threadedto receive a stem 6 having a central passage 7 forming a part of theconduit and communicating through a radial passage 8 with an annularspace 9 formed between the inner wall of coupling 5 and the periphery ofstem 6. This space 9 communicates through a narrow annular passage l0with the exterior of the device at a position just below the open end ofwhistle element II. The whistle element is threaded on the exterior ofstem 6, and by rotation of the element upon the stem, its positionrelative to passage l0 may be adjusted to vary the tone of the whistle.A cap [2 is threadedly connected to the upper end of stem 6 and providesa cap for a pressure adpressure is above a pre-selusting screw I3 to behereinafter more fully described. It is contemplated that the cap l2 andwhistle element ll may be integrally formed but the two piecearrangement is preferred in order that screw l3 can be adjusted withoutdisturbing the whistle setting. Also, the cap in this arrangement actsas a jamb nut for the whistle element.

It is to be understood that the entire whistle and valve arrangement maybe located at a great distance from the vessel protected and connectedthereto by a pipe connected to the lower end of coupling 5 or thepassage 8 may lead to a whistle element that is located remote from thevalve mechanism controlling passage 7.

A valve assembly is housed within the conduit and more particularlywithin coupling 5 which controls flow through passage l. This assemblyincludes a seat [4 formed on the lower end of stem 6 and a valve memberl adapted to engage the seat to control flow through the conduit.Inasmuch as the valve member is located in the conduit upstream from theseat [4, the pressure to be controlled urges the valve member towardseated position. A resilient means, which may include a coil spring I6,is arranged to urge the valve member l5 ofi of its seat.

The resilient means referred to preferably is such as to provide anadjustable force tending to unseat the valve member, in order that thepressure at which the alarm will be energized may be adjusted orselected. In order to accomplish this, the spring may abut the lower endof spacer El extending axially within the central passage through stem6. The other end of the spacer abuts the lower end of pressure adjustingscrew i3 which is threaded through the upper end of stem 5. The screwmay carry a jamb nut [9 adapted to lock the adjusting screw in aselected position. With this arrangement, rotation of the adjustingscrew will change the compression on coil spring Hi to vary theunseating force acting against valve member 15.

The valve assembly includes a means for imparting a reseating forceagainst the valve mem-I ber when flow of fluid is established throughthe conduit. This reseating means may in addition serve as a choke tosubstantially limit flow through the conduit whereby the alarm is verymiserly of the pressure fluid in the system protected. This means mayinclude a pressure responsive member as, for example, a piston-likemember or sleeve slidably mounted within the conduit.

The inner wall of coupling 5 is provided with two cylindrical portions2| and 22 joined to-,

gether by a tapered seat portion 23. The pressure responsive member 28is provided with cor-.

responding outer peripheral portions. The crossseotional area ofcylindrical portion 22 is greater than the area across seat I4 so thatthe pressure controlled, acting against the lower end of sleeve 20, uponopening of valve [5, forces the sleeve in a direction to return ball 15to seated position.

It is preferred to provide the valve member and pressure responsivemember as separate parts. A weak spring 24 may be employed between thevalve member and sleeve 23 whose purpose is to return sleeve 20 toseated position against seat 23 when the valve member is in seatedposition and the pressure has equalized about the sleeve. This seatingof the sleeve is more of a stop and does not positively provide a seal.Spring 24 may have only sufficient strength for this purpose. Thearrangement is such that the tapered shoulder 25 within the socket ofsleeve 20 engages ball IS, on unseating of the ball, so that movement ofthe sleeve under the influence of the pressure differential whichdevelops across the sleeve, when the valve member is unseated, returnsthe valve member to seated position.

The narrow diameter cylindrical portion of sleeve 20 should have a closefit within portion 22 of the conduit. The looseness of this fit Willafiect the frequency of the sounded alarm and also will govern to alarge degree the amount of pressure fluid lost due to the giving of thealarm. The clearance between the sleeve and cylinder 22 should be suchas to permit free sliding movement of the sleeve within the conduit, butshould be such as to provide a very small annular orifice to materiallyrestrict the flow of fluid therepast. In any event, the area of thisorifice should be materially less than the area within seat I4. Thislatter is true in order that the pressure downstream from the sleeve,upon unseating of the valve member, will quickly vent to provide apressure differential for actuating the sleeve.

By way of example only, but not by way of limitation, certain dimensionsfor the O. D. of the sleeve and the I. D. of cylinder 22 will be givenwhich have been found entirely satisfactory for use upon a whistle typelow pressure alarm for air resorvoirs commonly found in connection withcompressed air system. Where the I. D. of the conduit within cylindricalportion 22 ranges between .514 inch and .516 inch, the O. D. of thesleeve may range between .511 inch and .512 inch. Due to the annularcharacter of the orifice thus provided and to the constant movement ofsleeve 20 when an alarm is given, there is very little likelihood of thesmall area orifice becoming clogged with debris or the like.

In operation, it will be assumed that the coupling 5 is connected to agas pressure system to be protected, in order that occurrence of a lowpressure within the system will be called to the attention of the personin charge of the system. Assuming that the pressure within the system isabove the preselected set point for the giving of the alarm, the valvemember IE will be held against seat I4 and the pressure will beequalized on both ends of sleeve 2a because seat 23 does not provide anabsolute seal. The valve member will be subjected to the force of thespring tending to unseat the valve and the force of the pressurecontrolled holding the valve seated. Then as the pressure reduces withinthe system protected, it will also reduce about valve 15 because seat 23does not provide a perfect seal. Thus the seating force reduces, andwhen this is overcome by the constant pre-selected force of theresilient unseating means, the valve member will move oif of its seat.In the embodiment shown, the ball [5 will drop into the socket of sleeve20 and be held against shoulder 25 by the force of spring [6.

With the valve opened, the pressure downstream of sleeve 20 is quicklyvented creating a pressure differential across the sleeve. The fluiddischarged by this venting sounds the alarm. The differential will besubstantially the same difierential to which the seated valve member wassubjected at the time the valve was forced from its seat. However, dueto the greater crosssectional area or eifective area of the sleeve, aforce will be exerted against the valve member tending to seat it, whichis greater than the force due to the resilient unseating means. Thus,the valve member will be automatically and quickly returned to seatedposition. The alarm is sounded during this interval when the valvemember I5 is opened, for a rush of fluid through the interior of stem 6,passages 8, 9 and I9 and into and about the whistle I I will cause theemission of a shrill sound.

When the valve member is seated again by sleeve 20 subjected to thepressure within the system protected, the pressure will quickly equalizeabout the sleeve and the weak spring 24 will return the sleeve towardshoulder 23 which limits its travel away from seat [4. As long as thepressure of the system protected is below the set point of the resilientunseating means, the valve member [5 will again be unseated and thereseating operation will repeat. The affect of this will be a resultingintermittent shrill whistle which will continue as long as the pressurewithin the conduit is less than the pressure setting on spring I 6, butis great enough so that the force of the pressure against sleeve 20 willovercome spring I6. On the other hand, when the pressure drops belowthat point at which it will return sleeve 26 against the spring, acontinuous whistle will sound and this will indicate to the operator ofthe pressure system that the pressure has fallen below not only the setpressure but some lower preselected pressure. On the other hand, whenthe pressure within the conduit increases to one greater than thesetting of spring E6, the valve member I 5 will remain in seatedposition when returned thereto by sleeve 20 under the influence of thepressure controlled.

The diameter of sleeve 29 and the strength of spring It may be selectedso that when the conduit pressure upstream of sleeve 20 falls below apre-selected-low value, the spring IE will urge the sleeve against seat23 closing off the conduit to prevent further dissipation of gas fromthe system. Still seat 23 will not provide an absolute seal, but willreduce the rate of flow of fluid therepast far below the rate requiredto blow the whistle. The slight leakage past seat '23 is entirelysufficient to allow the pressure within the chamber about valve l5,which is of small capacity relative to the volume of the systemprotected, to reflect substantially the pressure within the system,which in turn will normally rise or fall slowly. Of course, in any eventsleeve 20 will not seat until an entirely adequate alarm has been given.

It will be seen that the objects of this invention have beenaccomplished. There has been provided a fully automatic low pressurealarm which will give an alarm when the pressure within a pressuresystem drops below some preselected value and which will automaticallydiscontinue the alarm when the pressure within the system rises abovethis value. The construction is such that very little pressure fluid isdissipated from the pressure system because of the giving of the alarm.The arrangement is such that an alarm will be given as long as thepressure within the system resides within a preselected low pressurerange but that the character of the alarm will change when the pressurewithin the system falls below an intermediate value in the range. Uponoccurrence of a pressure within the system less than the lower limit ofthe range, the valve mechanism may be arranged so as to close preventingfurther dissipation of gas, but this does not. occur until an adequatealarm has been given.

It will be understood that certain features and subcombinations are ofutility and may be employed without reference to other features andsubcombinations. This is contemplated by and is within the scope of theclaims.

As many possible embodiments may be made of the invention withoutdeparting from the scope thereof, it is to be understood that all matterherein set forth or shown in the accompanying drawings is to beinterpreted as illustrative and not in a limiting sense.

The invention having been described, what is claimed is:

1. A low pressure alarm for pressure systems comprising a conduitconnectable with the System, fluid actuated alarm means connected to theconduit and actuated by fluid flow therethrough, a valve assemblycontrolling flow through the conduit in response to the pressure thereinupstream of the assembly, said assembly including a seat in the conduit,a valve member disposed upstream thereof and urged thereagainst by theline pressure, a first resilient means urging the valve member towardopen position with a preselected force, a pressure responsive memberhaving an effective pressure area greater than the area across the valveseat movable with respect to said valve member, said pressure responsivemember exposed to the pressure within the conduit upstream of the valvemember and substantially restricting the conduit whereby upon unseatingof the valve member the upstream pressure moves the pressure responsivemember toward the valve seat to force the valve member to seatedposition, and a second resilient means engaging the valve and pressureresponsive member and urging the valve and pressure responsive memberapart.

2. The alarm of claim 1 wherein the second resilient member is a weakspring which moves the pressure responsive member away from the valvemember when the valve member is seated.

3. The subcombination of a valve assembly for automatically controllingflow through a conduit in response to pressure conditions in the conduitcomprising, a valve seat in the conduit, a valve member upstream thereofurged against the seat by the upstream pressure, resilient means urgingthe valve member toward unseated position with a predetermined force,and pressure responsive means in the conduit upstream of the valvemember obstructing flow therepast to an amount less than the flow ofpressure fluid past the valve member when open to provide a pressuredrop across the pressure responsive member upon opening of the valve tomove it toward the valve seat, said pressure responsive member engagingthe unseated valve and having a pressure face of greater area than thearea of the valve seat whereby it will return the valve to its seat,resilient means disposed between and engaging the pressure responsivemember and valve urgin the pressure responsive member in an upstreamdirection to increase the volume of the chamber defined in part by thevalve seat and the pressure responsive member, said resilient meansbetween the valve and pressure responsive member being weaker than theresilient means urging the valve 01f its seat whereby the valve whencracked from its seat will move into engagement with the pressureresponsive member.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 257,069 Reznor Apr. 25, 1882 569,943 Shirley Oct. 29, 1896777,538 Puckett Dec. 13, 1904 842,160 Aikman Jan. 29, 1907 1,220,419Hawley Mar. 27, 1917 1,966,854 Eskilson July 17, 1934 2,041,198 McLeanMay 19, 1936 2,351,035 Grant June 13, 1944 2,372,408 Trick Mar. 2'7,1945 2,389,887 Baxter Nov. 27, 1945 2,404,924 Sacchini July 30, 1946FOREIGN PATENTS Number Country Date 374,332 Italy of 1939

